When doctors suggested that John might benefit from a cochlear implant, they agreed that he should be assessed to see if he was suitable. He had the operation when he was two, and he's now a confident and friendly child who goes to a mainstream school and loves musicals.

The latest instalment of this is in his parents' illustrated children's book, 'My Brother John', written from the perspective of their seven-year-old daughter, Caroline.

The book was designed to explain cochlear implants to other children, and to provide disabled children with a peer.

“People think that children get an implant and can hear straight away and start speaking,” says Gerard. “An implant isn't a miracle. They are not for everybody. They give you access to sound - learning to communicate through speech takes years of hard work from the parents as well as the child. What you learn is that hearing and listening are different things. With the implant John can hear a lot of things, but for him to learn language you have to make sure that he's listening.”

The family have learnt to sign; this allows John to communicate with those in the deaf community who don't speak. He lip-reads, too. Gerard and Joanne have also attended residential courses and recommend seeking out other parents of deaf children. “It's nice to go up to someone and say ‘How deaf is your child?' and for it not to be unusual,” says Joanne.

“His life isn't defined by his deafness," says Gerard, "and that's what we want to show.”

My Brother John is published by Squeeze Marketing, £4.99, and is available from Waterstone's. Visit Gerard's website for more information, or see our earlier post about the book.

CHILD DEAFNESS: FACTS AND FIGURES - As featured in The Times

Each year in the UK an estimated 840 babies are born with permanent, significant hearing loss.

About 350 are deaf enough to be considered for a cochlear implant, and each year a further 100 children become deaf and may benefit from an implant.

Deafness can be caused by hereditary factors, or by infectious diseases such as rubella, mumps, measles, the cytomegalovirus (CMV) or meningitis. It may also be due to a birth trauma, such as a shortage of oxygen in the bloodstream.

The first child in the UK to receive a cochlear implant did so in 1987. In 2007, 430 children and 360 adults were implanted.

There are 180,000 implant users in the world, including 6,000 bilateral users.

How cochlear implants work

A cochlear implant improves hearing by stimulating the auditory nerve electrically. It usually consists of a small sound processor, a transmitter located behind the ear, and implanted electrodes. The transmitter coil is held in place over the implanted receiver by a magnet.

In a healthy ear, sound waves are transmitted across the eardrum and through the middle ear to the inner ear or cochlear. Specialised cells within the cochlear convert these mechanical vibrations into electrical signals, which travel along the auditory nerve to the brain. Implants work by bypassing damaged cochlear hair cells and stimulating the auditory nerve.

Sound is picked up by a microphone worn on the outer ear and sent to a sound processor. This modifies the signal before returning it along a lead to a transmitter. The transmitter coil sends the signals, by radio wave, through the skin to the implanted receiver, which in turn sends them down the wire to the electrodes in the cochlea. When the electrodes receive the signal, they make a tiny current that travels along the auditory nerve to provide a sensation of hearing.

The internal parts of the implant are inserted under general anaesthetic. Four to six weeks later the speech processor is activated and programmed to suit the individual's needs.